The answer is simple, science. 

The first scientific method we use is electrostatic attraction. Have you ever rubbed a balloon on your head and then stuck that balloon to the wall or ceiling? That is possible because of static electricity. This same concept is used in electrostatic attraction.  First, we electrically ground the object that is to be coated, and then electrically charge the colored powder as it sprays out of the nozzle.  The powder coat spray is a fine flour-like dust, and the particles are drawn to the grounded surface, just like the balloon is to the ceiling.  This allows for an even, smooth, coating and removes the need for the liquid mess and mixing sticks of traditional painting. 

Once the coating of colored plastic powder is applied then the second scientific element is introduced.  That second element is heat.  Wet paint needs to dry, but powder coating needs a hot, constant temperature for the chemical reaction to take place.  So, instead of letting it sit in the sunlight, we bake it.  The newly coated items are passed through a curing oven that generally sits around 400°F.  This massive heat melts the powdered plastic particles together where they form long molecular chains which have a high cross-link density.  These molecular chains are what create that beautiful and durable finish.

There are various reasons why you would want to choose powder coating over painting. 

Paint has a habit of wearing out.  It fades, gets chipped, dries and peels, and so requires new coats periodically.  Application is necessary more frequently due to the varying weather conditions found in the great outdoors.  Because of their special mixture and heat treatment, powder coating colors stay vibrant longer, and the coating itself is more resistant to weather, and impact.  All these are true because of the durable, UV resistant plastic layer that is created during the heating process.  If something is powder coated you can be sure that it will not need a second coating anytime soon.

Another reason why powder coating is a desirable choice is because it is cleaner, not only for the application area, but also for the environment.  The leftover dust from the powder coat can be recycled and used again, and since it isn’t wet it is easy to clean up.  Additionally, the mixtures don’t cause extra waste that is hazardous for the environment like with traditional paint, and since there are no solvents in powder coatings there are basically zero VOC’s (Volatile Organic Compounds) released into the air as it ages.  Through the use of powder coatings we can decrease the carbon footprint, while still creating structures of color and beauty.